Gear pump with balanced pressure loaded thrust plate



Dec. 3, 1968 R. L. SISSON ETAL 3,413,927 7 GEAR PUMP WITH BALANCED PRESSURE LOADED THRUST PLATE Filed Dec. 21, 1966 a Sheets-Sheet 1 INVENTORS RONALD L. SISSON CARMEN H. 'SHREVE ATTORN E! 1958 R. slssoN ETAL EAR PUMP WITH BALANCED PRESSURE LOADED THRUST PLATE 5 Sheets-Sheet 2 Filed Dec. 21, 1966 FIG. 2

INVENTORS L. SISSON H. SHREVE RONALD CARMEN fizz/4.12 4,

ATTORNEY Dec. 3, 1968 R. 1.. SISSON ETAL I 3,413,927

EAR PUMP WITH BALANCED PRESSURE LOADED THRUST PLATE Filed Dec. 21, 1966 5 Sheets-Sheet 5 INVENTORS RONALD L. SISSON CARMEN H. SHREVE fiqz K414 L,

ATTORNEY United States Patent 3,413,927 GEAR PUMP WITH BALANCED PRESSURE LOADED THRUST PLATE Ronald L. Sisson, Jackson, and Carmen H. Shreve, Niles,

Mich., assignors to Clark Equipment Company, a corporation of Michigan Filed Dec. 21, 1966, Ser. No. 603,467 Claims. (Cl. 103126) ABSTRACT OF THE DISCLOSURE Gear pump with thrust plate utilizing the pressure of the pumped liquid, in which the thrust plate is of bellows form defining a pressure cavity receiving the pumped liquid by which balanced pressure is applied against the gears.

Cross references This invention includes improvements over that claimed in our prior United States Patent No. 3,174,435 dated Mar. 23, 1965, assigned to the assignee of the present invention. Reference is also made to United States Patent No. 3,137,238, dated June 16, 1964, to Gordon, and assigned to the assignee of the present invention.

Disclosure In gear pumps, problems have long existed in sealing the gears in the housing, occasioned by a number of factors such, for example, as the differential in pressures as between the inlet and outlet of the pump, different pressures encountered in different installations, different viscosities of the pumped liquid, different temperatures involved, as well as possibly other factors. The construction of the present invention utilizes a semi-fixed thrust plate responsive to the pressure of the pumped liquid v working against the gears in predetermined areas of the gears, according to different pressures involved in the different areas of the gears, occasioned by the factors mentioned.

A broad object of the invention is to provide, in a gear p ump, such a thrust plate of bellows construction arranged for receiving the pumped liquid in its interior, and expanding in response to the pressures of the pumped liquid for providing a balanced thrust plate and thereby effectively sealing the gears.

Another object is to provide a construction of the general character just referred to in which the bellows thrust plate has an aperture communicating with the outlet passage whereby the pumped liquid is forced from the outlet passage into the interior pressure cavity of the thrust plate as referred to, and further in which the thrust plate engages the gears throughout the end surface of the gears, and wherein pressure actuated areas are distributed over that portion of the end surface of the gears necessary for compensating for other forces tending to prevent effective sealing of the gears.

Another and more specific object is to provide a thrust plate construction of the general character referred to above which is all-metal, whereby to enable it to be used with a maximum number of kinds of liquids, such as chemicals, without danger of attack by those liquids.

Still another object is to provide a thrust plate of the foregoing general character that is extremely effective for its intended purpose, and well controlled.

A still further object is to provide a thrust plate of the foregoing general character which is extremely simple and inexpensive to manufacture.

Other objects and advantages of the invention will appear from the following detail description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a sectional view of a gear pump incorporating the thrust plate of the present invention, taken in the plane containing the axes of the two gears;

FIGURE 2 is an end view from the left of FIGURE 1 but with the near housing cover removed, and showing the thrust plate in the plane of line 22 of FIGURE 1;

FIGURE 3 is a face view of the novel thrust plate from the side opposite that shown in FIGURE 2, showing the thrust plate inthe plane of line 3-3 of FIGURE 1; and

FIGURE 4 is a sectional view, on an enlarged scale, taken at line 4-4 of FIGURE 3.

Referring in detail to the drawings a pump embodying the thrust plate of the present invention is indicated in its entirety at 10 and includes a housing 12 made up of three main parts, namely, a central housing member 14, a rear cover assembly 16, and a front cover assembly 18. The pump also includes a driving gear 20 and a driven gear 22 working in chambers 24 and 26.

The gears in the present instance have integral shaft elements 28 and 30 journalled in the rear and front cover assemblies by means of suitable bearings 32. The driving gear 20 also has a shaft extension element 34 for connection with a suitable driving device. Similarly the driven gear 22 is provided with shaft elements 36 and 38 journalled in the rear and front cover assemblies in suitable bearings 40. The bearings 32 and 40 may be lubricated by any suitable means, the drive shaft element 34 may be sealed by suitable sealing means 42, and the housing sections may be sealed by suitable gaskets 44.

The gears 20 and 22 engage and are sealed by a fixed rear thrust plate 48 of suitable kind, gripped between the gears and the inner face 50 of the rear cover assembly 16. This fixed thrust plate 48 receives the thrust in that direction from the gears by a semi-fixed thrust plate 52 constituting the principal feature of the: present invention. The construction of the thrust plate 52 and its mounting in the housing are described in detail below. The pump housing 12 also defines an inlet passage 54 and an outlet passage 56 communicating with the gear chambers 24 and 26.

The thrust plate structure 52 is of composite, laminated form, and includes a pressure plate 58 defining an inner sealing surface 60 directly engaging the gears throughout the area of the latter. It also includes a bellows plate or member, or bellows structure per se, 62 mounted to the pressure plate 58, these two elements together constituting the thrust plate. The thrust plate is all metal, of suitable kind, the specific character thereof not being pertinent to the present invention; the pressure plate 58 would have highly wear-resistant characteristics, of steel-clad bronze, for example, while the elements making up the bellows member 62 would have such characteristics as to resist damage by flexing, at least one of the elements thereof flexing in the operation of the device as will be referred to :again hereinbelow. Additionally, all of the metals are preferably of such characteristics as to withstand attack, to the extent possible, from the liquids being pumped, such as chemicals.

The pressure plate 58 and the bellows member 62 are preferably of the same size and shape in plan, as shown in FIGURE 3, and have apertures 64 for receiving the shaft elements 30 and 38. The thrust plate is preferably of such size as to be gripped around its edge between the front cover assembly 18 and the face 66 of the central housing member 14, and it is also gripped between the front housing assembly and the hubs 66 and 67 of the gears. The thrust plate, due to this gripping, effectively seals the gear chambers although it is not essential that it be gripped at its marginal edge.

The bellows member 62 is made up of a pair of congruent plate elements or sheets 68, 70 of relatively thin metal of diaphragm thickness, secured together, as by electron beam welding, along a continuous line 72, in the instant case generally in the form of the figure 3 enclosing and defining a pressure cavity 74 therewithin for receiving liquid, extending throughout the area sursounded by the weld line. The pressure plate 58 is provided with an aperture 76 and the inner plate or element 70 of the bellows member 62 is provided with a similar aperture 78 in register therewith surrounded by a flange 80 which is crimped, in liquid-sealing engagement, over a cooperating flange 82 on the pressure plate 58 formed by a counterbore in the aperture 76, forming a composite but unitary structure. On the opposite side of the structure is another aperture 84 extending through the pressure plate and both elements of the bellows member.

The thrust plate is put into position with the sealing surface 60 thereof directly engaging the gears, and with the aperture 76, 78 in constant communication with the outlet passage 56, and thereby communicating with the liquid under the pressure of the load being worked upon by the pump. The liquid there is enabling to flow through the aperture into the pressure cavity 74 in the interior of the bellows member.

The aperture 84 on the opposite side of the thrust plate is in constant communication with the inlet passage 54, and thus the pressure condition in the inlet passage is transmitted through to the opposite side of the thrust plate. The outer or front surface 87 of the bellows member may also be termed a motive surface.

A quite complete explanation of the functioning of a gear pump and the problems involved therein is set out in the Gordon patent identified above; as explained in that patent, the pressure in the outlet passage, as propagated rearwardly from the load being worked upon, works backwardly through the gear teeth pockets 88 in diminishing amounts from one pocket to the next, throughout a substantial portion of the periphery of the gears. A point is reached where the liquid pressure is neutral although the exact location of this point is not critical, usually varying under different circumstances. However, there is a region where that pressure is neutral and under an average of a wide variety of circumstances that loca tion can be calculated. As set out at length in that patent, it is extremely diflicult to apply proper pressure to the thrust plate at the selected portions thereof according to the differential or gradient pressure in the gear teeth pockets. If only sufficient pressure were applied to the thrust plate according to the lesser pressure in the gear teeth pockets, there would be leakage under conditions of greater pressure, while if constant pressure were applied entirely over the thrust plate according to the greatest pressure in the gear teeth pockets, the wear on the parts would be too great. It is therefore desired that the pressure be applied to the thrust plate according to the outlet pressure. In that patent that result was accomplished by applying the liquid on the outer side of the solid thrust plate, while the present instance it is accomplished by applying the liquid in the pressure cavity 74.

In the present structure, the region of neutral pressure is represented by the extremities of the pressure cavity 74 as determined by the terminal elements 89 of the figure 3 (FIGURE 3) beyond which, within the confines of the bellows member, is a space indicated genorally at 90 which is neutral, i.e., the two elements of the bellows member are inactive from a pressure standpoint, and from a practical standpoint may be non-joined. The pressure cavity 74 therefore coincides with, and in the present construction overlies, that portion of the gears in which the pressure in the gear teeth pockets 86 is positive. In the remaining gear teeth pockets overlain by the area 90 there is a neutral or negative pressure, transmitted from the pressure in the inlet passage, this negative pressure being transmitted through the aperture 84 to the outer or motive side of the thrust plate.

In the normal operation of the pump, the liquid in the outlet passage 56 is forced through the aperture 76, 78

into the pressure cavity 74, the actual movement of the liquid, however, being very slight. This pressure upon build-up in the pressure cavity expands the bellows elements 68, 70 relatively, the outer element 68 engaging the front cover assembly and thus being immovable, the expansion of the bellows member being exemplified therefore by the movement of the inner element 70 which Works against the pressure plate 58 and forces it against the gears as stated. The inner element 78 is normally sprung out, self-biased against the wear plate and maintaining a preload condition.

Due to the coincidence of the shape of the pressure cavity 74 with the portion of the gears where positive pressure in the pumped liquid is developed, the pressure in the pressure cavity expands the bellows member in the same area in which the positive pressure exists. The pressure in the pressure cavity 74 is substantially uniform throughout the cavity so that the total force exerted on the inner bellows element 70 in inward direction is greater than that exerted outwardly by the pressure in the gear teeth pockets remote from the outlet passage, with the result that the element 70 is retained in full sealing engagement throughout its area with the gears. Since the extent of movement of the inner bellows element 70 is slight, as stated, the gripping of the peripheral margin of the thrust plate between the housing members does not appreciably interfere with the flexing movement of the bellows element 70. Additionally, the pressure plate 58, although preferably thicker than either of the elements of the bellows member, is enabled to move or flex sufficiently to provide the desired sealing action on the gears.

The thrust plate structure is extremely efiicient and effective, the pressure exerted in the pressure cavity being in direct proportion to the pressure in the outlet passage, and substantially of the same pressure, whereby to accurately counteract the pressures developed in the outlet passage.

Regardless of any differences in pressures involved because of any of the factors referred to, the effectiveness of the device remains uniform, different viscosities, or different temperatures, may cause different gradients as between the inlet and outlet passages, or between the successive gear teeth pockets, but regardless what factors come into play, the pressure exerted in the pressure cavity is proportional to the pressure in the outlet passage.

The bellows member 62, and the entire thrust plate, is of extremely simple construction and correspondingly inexpensive. The fact that the pressure cavity 74 is a single continuous space results in well controlled application of the intended pressure on the pressure plate 58.

While we have disclosed herein a preferred form of the invention, it will be understood that changes may be made therein within the spirit and scope of the appended claims.

We claim:

1. A unitary and self-contained thrust plate comprising a flat bellows member for operative interpositioning between and sealing engagement with opposed planar members and including a pair of plate elements fitted together in face-to-face relation and effectively integrally bonded together along a continuous line surrounding and defining a single pressure cavity between the plate elements, one of the plate elements having an aperture communicating with the pressure cavity and the plate elements being capable of limited movement toward and from each other throughout substantially the area of the pressure cavity, from a collapsed position in which the plate elements are substantially planar in form and substantially in 'face-to-face interengagement, to an expanded position in which they are separated from each other substantially throughout the area of the pressure cavity.

2. The construction set out in claim 1 which includes apertures for gear shafts, and in which the pressure cavity extends from one side of the thrust plate around and between the gear shaft apertures an extent greater than half the distance to the other side.

3. The construction set out in claim 1 and including a pressure plate secured to the bellows member, the plate elements of the bellows member being relatively thin and flexible and the pressure plate being relatively heavy and rigid.

4. The construction set out in claim 3 in which said aperture is formed in the plate element adjacent to the pressure plate, the pressure plate has an aperture in register therewith, and that adjacent plate element is provided with a flange surrounding the aperture therein crimped in liquid sealing engagement with the marginal edge of the aperture in the pressure plate.

5. The construction set out in claim 1 in which the pressure plate and bellows member are formed completely of metal.

6. The construction set out in claim 1 in which the plate elements of the bellows member are normally sprung apart whereby to provide a preloaded condition.

7. In a gear pump including a housing defining gear chambers and an inlet passage and an outlet passage communicating therewith, the pump also including intermeshing gears operatively disposed in the gear chambers, and the gear pump producing positive pressures in the outlet passage which are transmitted in progressively diminishing elfect toward the inlet passage, the pump housing also including sections detachably secured together, a unitary and self-contained thrust plate comprising a fiat bellows member including a pair of plate elements fitted together in face-to-face relation and effectively integrally bonded together along a continuous line surrounding and defining a single pressure cavity between the plate elements, one of the plate elements having an aperture communicating with the pressure cavity and the plate elements being capable of limited movement toward and from each other throughout substantially the area of the pressure cavity, said thrust plate being incorporated in the housing in pressure-active position between the gears and a fixed element of the housing, and said aperture being in constant communication with the outlet passage.

8. A thrust plate according to claim 7 wherein the thrust plate is of greater dimensions than the gear chambers and is gripped between the housing sections at its periphery beyond and around the gear chambers.

9. The thrust plate in conjunction with the pump as set out in claim 7.

10. A construction according to claim 7 and including a pressure plate secured to the bellows member, the plate elements of the bellows member being relatively thin and flexible and the pressure plate being relatively heavy and rigid, and wherein the pressure plate faces and engages the gears of the pump.

References Cited UNITED STATES PATENTS 2,816,512 12/1957 Murray 193-126 2,853,952 9/1958 Aspelin 103-l26 2,967,487 1/1961 Nagely 103126 3,050,010 8/1962 Thrap et a1. 103-126 3,101,673 8/1963 Clark et a1 103--126 3,131,643 5/1964 Marietta 103--126 3,137,238 6/1964 Gordon 103--126 3,174,435 3/1965 Sisson et al 103-426 3,213,799 10/1965 Trick 103-426 3,294,029 12/1966 Clark et a1 103 126 3,172,369 3/1965 Ballu 103150 0 FRED C. MATTERN, 1a., Primary Examiner.

WILBUR I. GOODLIN, Assistant Examiner. 

